Abstract:

The effect of nitrogen on rice protein contents has been widely studied, but the accumulation dynamics of protein components of superior and inferior grain in large-panicle rice and their responses to nitrogen are limited reported. In this study, two indica-japonica hybrid rice were used as materials, and four nitrogen rates, namely, N0 (no nitrogen application), low nitrogen (100 kg·hm^-2), medium nitrogen (200 kg·hm^-2), and high nitrogen (300 kg·hm^-2) were adopted to compare the characteristics of yield, grain types, grain weight and storage protein accumulation in superior and inferior grains. The results showed that nitrogen application significantly increased the yield, protein content for two cultivars, but there were differences in response to nitrogen. Yongyou12 obtained a high yield under low nitrogen, and its protein content was stable under different nitrogen treatments, which can get a balance of high yield and good quality. Low nitrogen had no significant effect on grain type, while high nitrogen reduced the ratio of length to width with a small extent, resulting in a slight decrease in grain weight. There was a compensatory effect between prolamin and glutelin accumulation, thus maintaining the relative balance of storage protein. Although the protein concentration of inferior grain was higher than that of superior grain, the total content was still significantly lower than that of superior grain due to its small grain weight. The storage protein is mainly located in the outer endosperm of grains, and Yongyou17 is more sensitive in response to nitrogen than Yongyou12. The obtained results can provide a theoretical basis for the high yield and good quality cultivation techniques of indica-japonica hybrid rice.

Key words: indica-japonica hybrid rice, protein components, grain type, superior and inferior grain, nitrogen